From f6e9af87661530e60d9faf1d96675e8f22127aa8 Mon Sep 17 00:00:00 2001 From: Eric Biggers Date: Sun, 31 Mar 2019 13:04:21 -0700 Subject: [PATCH] crypto: arm64/cbcmac - handle empty messages in same way as template My patches to make testmgr fuzz algorithms against their generic implementation detected that the arm64 implementations of "cbcmac(aes)" handle empty messages differently from the cbcmac template. Namely, the arm64 implementations return the encrypted initial value, but the cbcmac template returns the initial value directly. This isn't actually a meaningful case because any user of cbcmac needs to prepend the message length, as CCM does; otherwise it's insecure. However, we should keep the behavior consistent; at the very least this makes testing easier. Do it the easy way, which is to change the arm64 implementations to have the same behavior as the cbcmac template. For what it's worth, ghash does things essentially the same way: it returns its initial value when given an empty message, even though in practice ghash is never passed an empty message. Signed-off-by: Eric Biggers Signed-off-by: Herbert Xu --- arch/arm64/crypto/aes-glue.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/arch/arm64/crypto/aes-glue.c b/arch/arm64/crypto/aes-glue.c index 692cb75f2ca2..f0ceb545bd1e 100644 --- a/arch/arm64/crypto/aes-glue.c +++ b/arch/arm64/crypto/aes-glue.c @@ -707,7 +707,7 @@ static int cbcmac_final(struct shash_desc *desc, u8 *out) struct mac_tfm_ctx *tctx = crypto_shash_ctx(desc->tfm); struct mac_desc_ctx *ctx = shash_desc_ctx(desc); - mac_do_update(&tctx->key, NULL, 0, ctx->dg, 1, 0); + mac_do_update(&tctx->key, NULL, 0, ctx->dg, (ctx->len != 0), 0); memcpy(out, ctx->dg, AES_BLOCK_SIZE); -- 2.30.2